Protesters planning to behead effigies of Prince William, the Queen, Charles and Camilla were arrested last night and held in a south London police station during the wedding.

Police seized a working guillotine as they arrested Chris Knight, 68, head of anti-royal anarchist group The Government of the Dead; his partner Camilla Power, also 68, and Patrick Macroidan, 45, dressed as an executioner, at Knight's home in Brockley.

They were held for conspiracy to cause a public nuisance and breach of the peace. They claimed they were intending to stage a street theatre event. Sources said they were expected to be released on bail at about 3pm today.

In a separate development, activist Charlie Veitch was held in Cambridgeshire on behalf of the Met, on suspicion of conspiracy to cause a public nuisance and breach of the peace. The privately educated former finance worker was among activists who occupied Fortnum & Mason during last month's TUC march.